Gas turbine engines usually include bleed valves in the engine casing forward of the burner which, when an engine surge is imminent, open to rematch the compressor stages. Valves including ports in the compressor casing which open via a movable valve element are often used, and valves removable from the outside of the engine are desirable for ease of maintenance.
Typical bleed valves include a valve element selectively movable to an opened position where it protrudes in the bypass flow path to open a port in the bypass flow path wall communicating with the primary flow path, such that fluid from the primary flow path can be evacuated to the bypass flow path. The protruding valve element in the bypass flow path can produce perturbations within the bypass airflow which are detrimental to engine performances.